Loons, along with other waterfowl, are at the mercy of environmental and climatological changes going on in the Great Lakes.

Four times in the last seven years, migrating waterfowl in the Great Lakes basin, especially common loons, have experienced massive die offs during their fall migrations. These anomalies, if unchecked, can have dangerous repercussions for the survival of Michigan loons into the next decade.

But, for better and for worse, based upon an array of environmental and climatological conditions, one can set their clock by when the die offs take place. The next step, biologists say, is finding preventative measures to deal with those conditions to preserve a species already threatened in the state. The problem is, at this point, solutions are hard to come by. Unfortunately, the loons, a symbol of northern lakes and wild places with their eerily lonely two-note call, serve as the end result sentinel of a growing environmental danger in the Great Lakes.

According to the United States Geological Survey (USGS), there are about 30,000 common loons in the United States. During the breeding season, from early spring to late fall, about half of them reside in the Great Lakes’ states of Michigan, Wisconsin and Minnesota.

In 2012, thousands of dead birds, mainly common loons washed up dead on Lake Michigan shorelines – from the Upper Peninsula, down to the Sleeping Bear Dunes National Lakeshore. A large percentage of the dead loons had just entered their first year of breeding maturity. While the mortality rate in 2012 was the worst on recent record, it followed similar incidents that took place in 2006, 2007 and 2010. Northern Lake Michigan serves as a staging area for common loons from the Great Lakes states and Canada to load up on food before flying down to their wintering grounds in the Gulf of Mexico and the southern Atlantic Ocean.

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In 2013, early indications are that the death count numbers are way down. Most bird count volunteers up and down the Lake Michigan shorelines in both the Upper Peninsula and the Lower Peninsula report only small numbers of dead birds, many likely from natural causes, although carcasses are being analyzed. The largest number of deaths thus far this year appears to be in the Sleeping Bear Dunes National Lakeshore, a regular hotspot during the largest die offs. So far this year, 272 dead birds, mainly red-breasted mergansers, ring-billed gulls and white-winged scoters, have been identified along the 32-mile shoreline, according to Dan Ray, a biological technician and project leader for the avian botulism monitoring program for Sleeping Bear Dunes National Lakeshore. And of that number, only nine of the dead are common loons, but Ray cautioned that since loons spend most of their time miles off shore in open water, it’s possible that others have died but simply haven’t been washed to shore. USGS airial surveys in September and October indicated distribution of loons similar to previous years.

Last year at Sleeping Bear, more than 1,500 birds were found dead, including 600 loons.

In 2012, in just a seven-mile stretch of Lake Michigan beach near the Upper Peninsula town of Gulliver, 865 water birds showed up dead in a two-week period in October, 302 of which were common loons. That came to an average of 121 dead birds per mile. In 2013, there has been virtually nothing.

The botulism problem

The culprit in each of these outbreaks is Type E botulism, a paralytic condition brought on by the consumption of the botulinium neurotoxin. This neurotoxin is thought to be produced under oxygen-depleted conditions -- like what takes place when huge Cladophora algae mats build up on the lake bottom and decompose. When enough bacteria is developed, the toxin is released. That is just the first step in what becomes toxin production and a toxin food chain transfer from the botulism to the waterfowl.

The Type E botulism toxin is then consumed by bottom-feeding insect larva and invasive species such as quagga mussels and zebra mussels. The mussels also consume plankton floating in the water column and then excrete waste into the dead algae mat, feeding the bacteria. The mussels are then consumed by the round goby, another invasive species. And finally, the gobies, more prevalent in the Great Lakes every year, are consumed by waterfowl in mass quantities.

“That’s what we believe is going on. It’s a fair guess, but it’s still a guess,” said Jennifer Chipault, a USGS biological technician. “Data is still being gathered from the field.”

The common loon, after arriving in the northern part of Lake Michigan to start its migration, feeds on the gobies and ingests the toxin. The botulism affects the bird’s nervous system and musculature, leaving it unable to fly. Soon, it can no longer keep its head aloft, and it drowns.

According to Dan Ray, the telltale signs of Type E botulism toxin poisoning are clear. First, the infected birds begin to have problems with their wings, primarily an inability to fold them into their bodies. As that problem persists, they become weak and are unable to fly. Next, they will bob their heads up and down in a desperate attempt to breathe. In the final stages, they become too weak to lift their heads up. Some dead birds on the shore are found with their bills still stuck in the sand. In the case of common loons, since most of their time is spent miles off the shore in open water, when they are unable to keep their heads aloft, they drown. The drowning kills them before the toxins can finish them off. Most dead loons are only discovered after their bodies are blown to shore by prevailing winds.

But analysis of sediment cores from near Sleeping Bear Dunes show that Type E botulism bacterium has long been in the Great Lakes. The Cladophora algae is a native species. So why is botulism suddenly causing mass deaths among migrating waterfowl?

According the biologists studying the issue, it goes back to the integration of the invasive mussels into the Great Lakes basin via ship ballast.

Since 1988, when the first zebra mussels, native to the Caspian and Black seas, were found in Michigan in the St. Clair River, the invasive mussels have been clearing and “cleaning” Great Lakes water columns by consuming plankton. Aesthetically, their work gives the water a more pleasing appearance, but also allows the sun’s rays to penetrate deeper into the water column, causing larger and larger algae mats to flourish and then die on the bottom.

What follows is a precise recipe for disaster that includes unusually warm spring weather, a hot summer, low water levels and a lack of rain. The resulting warmer water temperatures provide a perfect environment for the Clostridium to grow. In other words, the spring and summer of 2012.

Warm weather sets the stage

According to the National Weather Service, March temperatures in areas like Negaunee, Iron River and Houghton in the Upper Peninsula, were an average of 20 degrees warmer in 2012, 49 degrees, than they were this year, which averaged 29 degrees. In Alpena, Rogers City, Pellston, Petoskey, Charlevoix and Traverse City in the upper Lower Peninsula, March temperatures were 15 degrees warmer in 2012, 42 degrees, than they were in 2013, which had an average of 27 degrees for the month. Those numbers mean the ice sheets on Lake Michigan melted much sooner than normal, removing the barrier that would otherwise block the sun’s rays and prevent algae from forming until much later. Temperatures were about 10 degrees warmer in the U.P. in April (50 degrees vs. 40 degrees) and about three degrees warmer at the top of the Lower Peninsula (41 degrees vs. 38 degrees). Rainfall in the U.P. was down dramatically in 2012 during the two months at the start of the spring compared to 2013, with an average of 1.9 inches of rain for March and April in 2012 compared to an average of 6.24 inches in 2013. In the upper L.P., rainfall in March and April was similar in 2012 and 2013 (4.7 inches vs. 5.7 inches on average), according to NWS numbers. Thanks to an increase in rain, lower temperatures and most importantly, less evaporation, lake levels are up six inches compared to last year, although they remain at historically low levels.

“It was certainly cooler and wetter than last year,” said Dan Myers of the Tip of the Mitt Watershed Council, whose volunteers monitor about 25 miles of shoreline in Charlevoix and Emmet counties. “A major factor was that it was really cold in the early spring and summer. Ice didn’t leave some of the inland lakes until late April, early May. In 2012, we had some 80-degree days in March.”

But there have been warm springs and hot summers before. And there have been cases of avian botulism, but nothing on this scale for decades. Avian botulism was first documented in the Great Lakes in the 1960’s, but there were very few confirmed cases in Lake Michigan between 1983 and 2006. The addition of the invasive mussels into the mix has provided an easier link in the food chain to deliver the toxins to the waterfowl.

“You must have toxin production and toxin transfer,” said Brenda Moraska Lafrancois, a regional aquatic ecologist with the National Park Service out of Ashland, Wisc. “This new factor (mussels) has been introduced, making both toxin production and transfer easier.”

“Mussels are a more efficient way to deliver the toxin into the food chain,” echoed Damon McCormick, co-director of a research group called Common Coast Research and Conservation in Houghton. He has been studying loons in the Upper Peninsula since 1997.

Effects of the 2012 die off

Much of McCormick’s work takes place in Seney National Wildlife Refuge, a protected area in the eastern-central Upper Peninsula. He sees firsthand the results of the devastation from last year.

From 1989 through 2004, the return rate of leg-banded adults who return to the refuge every spring has hovered around 96 percent. Since the four major die offs in the last seven years, the numbers have consistently gone down. This spring, following the devastation in 2012, only 76 percent of the banded adults returned, compared to the returns a year earlier.

“About a quarter of returns went missing,” McCormick said. “With loons, (who average about 0.4 surviving offspring per year from 1.5 eggs), it doesn’t have to be bad every year to devastate the population. Loons can’t make up for that.”

The average common loon lifespan is 25-27 years, with the probability that some live into their 30s and 40s. Last year’s die off consisted exclusively of mature adults and represented thousands of years of life. Those animals had a proven record of reproduction. Juveniles survived the die off during migration last year because they were not yet able to dive and hunt the infected gobies. But those birds still must survive their first three years in the Atlantic and the Gulf of Mexico, years which are fraught with peril from a variety of predators. On average, only about 60 percent of those birds survive that time period before they reach sexual maturity and head north near their birthplace to find a territory. So the worst results of the die off are yet to come.

“Suddenly, this spring, we had a refuge that was much more open,” McCormick said. “That’s largely an impact of the botulism. There wasn’t the same amount of birds looking for and fighting for their turf.”

Statewide, the last common loon survey in 2007 showed 800-900 pairs in Michigan, giving the bird “threatened” status. While no surveys have taken place since then, clearly the number of pairs is lower in 2013 since two mass die offs have taken place since 2007.

What can be done?

Finding a fix for reoccurring disasters is difficult. Lafrancois said biologists are limited in the kind of testing they can do in the lab because the Centers for Disease Control’s National Select Agent Registry restricts the amount of Type E botulism toxin and bacteria. Researchers can only have a half a milligram of the toxin in their labs and cannot culture the bacteria. So, establishing controls in the lab are limited, and researchers are left primarily to field data and testing the blood of carcasses.

“It’s a complex ecological problem, made more complex by Lake Michigan’s changing food webs, the transient nature of toxin production, the fact that many of the affected birds are migratory, and the restrictions on lab testing due to bioterrorism concerns,” Lafrancois said.

Lafrancois added some improved policies are in place to limit the introduction of new and existing Eurasian invasive species into the Great Lakes with more regulation of ballast procedures. For example, if ballast water is picked up in an area of fresh or brackish water, where both fresh and saltwater species can survive, the brackish ballast water is replaced with saltwater, which in theory kills all of the organisms in the ballast before moving into Great Lakes’ gateways, such as the St. Lawrence Seaway. Also, ballast water can be treated with technology, such as thermal methods, biocide or ultraviolet light. There is also some thought given to using a seismic shock system to kill the round gobies, but nothing has been instituted yet.

“Efforts to curb new species introductions may allow Great Lakes food webs to stabilize and give managers some time to come up with solutions,” Lafrancois added. “A lot is being done to reduce Cladophora growth for beach health and other reasons. Although we can’t control the weather, some attention to lake level management might be warranted.”

“We are limited in terms of a cure,” Ray said. “We are trying to focus on a moving target. As soon as one thing is understood, new factors come in. The best thing we can do now is to monitor the situation. Gobies are everywhere in the Great Lakes. They are a food base for a lot of other animals. It’s tough to come up with a species specific control.”

While the northern part of Lake Michigan seems to be the epicenter of avian botulism, it may not be. McCormick said northern Lake Michigan simply benefits from more monitoring, especially since it is a staging area for migrating birds. But he said there are other areas, the east coast of Lake Huron on the Canadian border, for example, that had a huge die off in 2010. He also suspects there are collections of dead loons in and around the many islands far out in open water in the Great Lakes. Those islands are popular areas for loon nests.

“There hasn’t been much systematic monitoring of the problem. With so little monitoring being done, it’s tough to determine the scope,” McCormick said.

McCormick calculates there are roughly 527 miles of Lake Michigan shoreline between the tip of the Garden Peninsula and the southern edge of Sleeping Bear Dunes National Lakeshore, including the shorelines of all the major islands within the northern portion of the lake (the Manitous, the Foxes, the Beaver Island cluster). He said in 2012, only 68.5 miles were regularly monitored. In those areas, 1,180 dead common loons were documented.

“While I don’t think it’s appropriate to simply extrapolate that average (17 dead loons per mile) to the entire 527 miles, it’s clear that even the most conservative of estimates should suggest there were several thousand dead loons in just the northern third of Lake Michigan last season.

“In terms of awareness, this year it was sort of out of sight, out of mind. This doesn’t have the same impact as an annual threat,” he added. “But for loons, it doesn’t have to be every year. If an average loon pair produces 0.4 chicks per year, age does matter, as does the survivorship of chicks and adults. It takes only a small change in variables to dramatically affect the population.”